When I look up pictures of naked guys I feel this weird feeling of heat and heart racing. Does anyone else experience this? It makes me very uncomfortable.

Is this an exposure exercise from your therapist? Of it is, asking for reassurance here makes the ERP exercise pointless. Response prevention is equally if not more important than the exposure. Sit with the uncertainty about what all of those feelings may or may not mean. If not, it sounds to me like what you’re doing is a pretty torturous compulsions: testing yourself with pictures to see if you have a reaction. And it’s one that will never give you the answer you want or reassure you in any lasting way. It’s just feeding the obsession and I’d encourage you to stop.

That's ocd for you... Ocd will do anything to "accuse" you of what your obsession suggests, to go so far even to make you feel fake arousal/feelings/thoughts /mental images just to scare you even more than you already are.

It's most likely because your anxious you might find them attractive

I’ve gone down that route and it doesn’t help. My heart raced, but not erection..eventually got bored... But that won’t be good enough..you’ll have to test yourself more and more. Just like “pureOlife” says..it’s just feeding your obsession. It’s better to just not go there at all and live your life...your sexuality will be clear just by living...you didn’t have to focus this hard to figure out you were straight right?

I know it’s not attraction, because the feeling is absolutely horrible. It’s that “what if” that gets me.

If** it is

Just dont stress about it